The invention relates to an absorbent article such as a sanitary napkin, an incontinence guard, or a panty-liner, which article has a substantially elongated shape with a longitudinal direction and a lateral direction and also exhibits two side edges, a front edge and a rear edge, a front portion and a rear portion, and also a crotch portion situated between the front portion and the rear portion, which article further exhibits a liquid-pervious surface layer and a liquid-impervious surface layer.
Conventional absorbent articles of the above-mentioned kind typically have a substantially flat shape. Since the lower abdomen of a woman typically does not exhibit a corresponding flat appearance, problems often arise both during application as well as during use of such articles. The contact of the article against the body becomes poorer and a gap easily forms between the article and the body of the user. This implies that there is a substantial risk of body exudate leaking out between the article and the body of the user.
In order to solve this problem, it has been proposed to bend the absorbent article in a longitudinal direction, so that it assumes the shape of an elongated liquid-collecting bowl. Such a shape conforms somewhat better to the body contour of the lower abdomen of a woman. Accordingly, in EP 155 515 it is disclosed how such an absorbent article is given a bowl-shaped appearance by means of the application of elastics in the longitudinal side edges of the article.
In WO 96/20679 an absorbent article is disclosed which comprises a resilient component and tensioning means in order to provide the article with a bowl-shaped appearance.
One problem with articles of the above-mentioned type is, however, that they do not conform to the anatomy of the user particularly well, but only exhibit a generally bowl-shaped appearance. In order to make them bendable by means of the elastic means, and in order not to cause discomfort to the user, the articles are manufactured from soft, flexible materials. This implies that they are easily deformed during use, which leads to even worse fit and possible leakage. It is, for instance, not unusual that the longitudinal side edges of the article are folded in over the liquid-receiving surface of the article, whereby the area accessible for absorption is considerably reduced. When sudden and heavy liquid flows occur, there is consequently a substantial risk that the liquid is not absorbed into the article, but instead flows onto the inwardly folded side edges and leaks out on the clothes of the user.
Another problem associated with an article of the above-mentioned type is that it does not fit well against the body and therefore does not stay in place in a natural way during use, but must be attached to the panties of the user by means of special attachment means such as glue-surfaces or the like. The contact of the article against the body therefore becomes largely dependent on the quality and the shape of the panties of the user. Since many women use their most worn-out panties during menstruation, the result will in many causes be poor contact against the body with entailing leakage of menstrual liquid.
Still another factor which affects the leakage security of such a known article is that the article, instead of being in contact with the body of the user when in use, tends to follow the movements of the panties when the user is moving. Due to this, the article may end up in an incorrect position in relation to the body. Apart from leading to an increased risk of leakage, the mobility of the article in relation to the body also implies that the user, in a very obvious way, is reminded of the presence of the article in the panties and thereby perceives the article as uncomfortable and indiscreet to wear.
One object of the present invention is to provide an absorbent article with high leakage security and good fit and user comfort. Still a further object of the invention is to provide an absorbent article which during use rests securely and comfortably in place in contact with the body of the user.
An article of the type discussed by way of introduction, in which the problems associated with such previously known articles have been essentially eliminated is, according to the invention, mainly characterized in that the article, at least within the front portion and the crotch portion, exhibits high bending stiffness against bending along bending lines extending in a transverse direction, whereby the front portion and the crotch portion of the article exhibit high shape permanence during use of the article, and also that the front portion of the article is inclined in relation to the crotch portion, in a direction towards the liquid-pervious surface, whereby the front portion forms an angle xcex1 with respect to the crotch portion which is substantially permanent during use.
Since the front portion of the article is angled upwards from the central portion so that the front portion of the article, in the longitudinal direction of the article, conforms in a better way to the shape of the mons veneris of the user, it is prevented that the article during use slides backwards on the user. During use, the angled front portion contacts the mons veneris of the user and functions as a stop plate which counteracts the article being fed backwards by the leg movements of the user. In order to obtain the desired braking function, it is necessary that the front portion and the crotch portion of the article are so stiff that the angle therebetween is essentially maintained even during use. For reasons of comfort, however, it may be convenient that the edge portions closest to the longitudinal sides of the article, and the front edge, respectively, are constituted by a less stiff material.
An article according to the invention is rigid to bending in a transverse direction, i.e. it resists bending along bending lines which extend in the transverse direction of the article. In this way, the article maintains the shape it has in the length direction during use. On the other hand, the article may allow for a certain degree of deformation by means of compression in the transverse direction. It may be an advantage if the article may adapt to some extent to the body movements of the user and to the gap between the legs of the user. Such deformation may be achieved in a controlled way if the material in the article is chosen in such a way that the edge portions of the article are soft and resilient, whereas a central, longitudinal portion of the article is stiff and incompressible. Another way of achieving controlled compression of the article is by means of providing it with longitudinal bending notches such as ridges, grooves, compressions, slits, or the like. It is an advantage if the compression of the article can take place with a certain elasticity, so that the article more or less resumes its original width when the compressive forces cease.
If, however, the article is designed so that its width at the narrowest point in the crotch portion does not exceed approx. 40 mm, and preferably does not exceed approx. 35 mm, it is possible to use articles which, when subjected to the forces which arise during use, are also completely rigid when bending along longitudinal bending lines.
Measurements have shown that all humans have a critical area in the groin portion between two muscle groups which extend from the inside of the base of the pelvis down along each thigh. The distance between the two muscle groups has thereby been found to be surprisingly similar for all individuals, independent of body shape and weight. Thus, the distance between the thighs of a user is of course affected by fatness, while the distance between the muscle groups in the crotch of the user is the same, independently of whether the user is thin, of normal weight or overweight. It has been shown that the fact which determines whether a user experiences discomfort in the form of pressure or chafing against the insides of the thighs is whether the absorbent article during use has a width which, in the critical area, considerably exceeds the distance between the muscle groups in the groin area. This distance has been found to be between approx. 30 mm and 35 mm, Furthermore, it has been shown that an article with a width which during use exceeds 40 mm in the critical area is perceived as uncomfortable by the majority of users. On the contrary, it is seldom perceived as unpleasant that an absorbent article presses against or displaces fatty tissue which may be present in the crotch area.
Where conventional deformable absorbent articles are concerned, the limited space in the crotch area of the user causes the articles to be compressed in an uncontrolled way between the legs of the user and to be creased in order to be accommodated between the groins. When an absorbent article according to the invention is concerned, having a very stiff shape element in the crotch portion, compression may only take place to a limited extent, whereby the degree of possible compression is controlled by the design of the stiff crotch portion. It is therefore essential that the width of the absorbent article in the crotch portion during use does not exceed the critical value which can be tolerated by the user.
It is, however, not necessary that the crotch portion has a width along its entire length which, during use, is less than 40 mm. Since the critical area in the crotch region of the user is approx. 5 mm to 15 mm long, it is sufficient if the part of the crotch portion, which during use is intended to be arranged within this area, fulfils the requirement of a maximum width. Accordingly, it is sufficient for the invention if, in the longitudinal direction of the article, there is a 5-15 mm long area in the crotch portion within which the width during use of the article is no larger than approx. 40 mm and preferably is no larger than approx. 35 mm.
The stiffness of an absorbent article is to a high degree dependent on the shape of the article, particularly the shape of those components which exhibit high stiffness. A stiffening member, having beams in the form of ridges or grooves, consequently has a higher stiffness perpendicularly to the extension direction of the ridges or grooves than a completely flat material. The beams may be achieved by means of forming the material itself, or by means of reinforcing it with strips or ribs of another material. Furthermore, the stiffness and the resistance towards bending and twisting may be increased by imparting a bowl-shape to the material, or by means of increased material thickness.
The desired stiffness may advantageously be achieved by means of providing the article with, for instance, a liquid-arresting cover layer on the side which is intended to face away from the user when the article is used, which cover layer, at least at the front and central portion of the article, may be constituted by a rigid plastic layer. Such a plastic layer may, for instance, be shaped by means of casting or vacuum forming into a stable shell, inside which an absorbent body is placed. Typically, the absorbent body is covered by a liquid-pervious cover layer on the side of the article which during use is intended to face the user. Depending on the structure of the absorbent body, it is however not always necessary to use a special liquid-pervious cover layer. Accordingly, for instance, an absorbent foam layer, or a layer of absorbent fibre fabric, so-called nonwoven material, may constitute a component of an absorbent body and at the same time serve as a liquid-pervious cover layer.
As an example of plastic materials which have been found to have sufficient bending stiffness and torsional rigidity in order to achieve the shape stability necessary for the invention, one can mention polyethylene or polypropylene having a layer thickness of at least 0,4 mm. The material stiffness of a plastic film which is suitable for use as a stiffening element in an article according to the invention should exceed 100 N, as measured in accordance with ASTM D 4032-82 xe2x80x9cCircular Bend Procedurexe2x80x9d, which method is described in detail in EP 0 336 578. In this context, material stiffness refers to the stiffness of a flat material layer.
When designing an absorbent article according to the invention, it is important to pay attention to the lower limit of the bending stiffness, since an article having a too low bending stiffness collapses when, during use, it is subjected to forces directed backwards. The upper stiffness limit is, however, not critical. On condition that an article according to the invention is given a shape which closely conforms to the body shape of the user, it has surprisingly been discovered that even extremely stiff and hard materials can be tolerated. Accordingly, it is, for instance, possible to use a shape-retaining insert of steel, aluminium, wood, or the like with such high bending stiffness that it does not permit deformation unless it is intentionally subjected to violence. Plates as well as rods and different types of skeleton-like constructions may be used.
It is not possible to specify a definite minimum value for the bending stiffness of flat materials which are suitable for achieving the desired stiffness of the finished article. Since a number of factors, beside the stiffness of the material itself, are of importance for the final stiffness of the article, the choice of material e.g. has to be adapted to the design of the article and to the stiffness of other components in the article.
One way of increasing the stiffness of a plastic layer is, by means of casting, bending, vacuum forming or in another way, to provide the stiffening element in the form of an originally flat material layer with a profile having elongated grooves, or ridges. Such a stiffening element exhibits a bending stiffness against bending perpendicularly to the extension of the grooves and ridges which is considerably increased in comparison to an untreated stiffening element. It is, of course, also possible to achieve increased stiffness by attaching stiffening material strips, rods, or the like, to the stiffening element. Furthermore, the stiffness of the article during use is affected if the crotch portion of the article is compressed in the transverse direction in the vicinity of the transitional area between the crotch portion and the front portion. Such compression namely increases the beam effect in the stiffening element and counteracts bending of the front portion in relation to the crotch portion.
Still another way of increasing the bending stiffness of a material layer is by laminating it with one or several additional material layers.
According to one embodiment of the invention, the front portion of the article is not only inclined with respect to the central portion, but is also curved in the longitudinal direction. In this manner, a better adaptation to the curved outline of the mons veneris of the user is achieved. In a corresponding way, the front portion may be curved in the transverse direction of the article, whereby the front portion assumes a bowl-shaped appearance which gives the article a very good fit around the mons veneris. By bending the front portion of the article in the longitudinal direction and/or in the transverse direction, a number of advantages are achieved. Accordingly, the improved fit causes the article to stay more securely in place during use, whereby leakage-security is enhanced. Furthermore, the anatomically adapted shape results in the article, although being very stiff, not being perceived as being uncomfortable to wear and does not protrude even under tight clothes. A further advantage with a bowl-shaped front portion is that the stability of the article and the resistance to deformation are increased. In particular, the resistance to compression in the crotch portion of the article is increased.
An anatomically designed article, according to the invention, is kept securely and comfortably in position against the body of the user during use, without the need for particular attachment means. This implies that the article is completely detached from the panties of the user, whereby the risk that the article moves with the panties during use, and thereby ends up in an incorrect position in relation to the body of the user, is almost completely eliminated.